Extended curable compositions for use as binders

ABSTRACT

The present invention provides low-cost formaldehyde-free curable aqueous compositions comprising 100 weight parts of one or more than one binder chosen from (i) mixtures of one or more than one polycarboxylic acid or polymeric polyacid and one or more than one polyol compound comprising at least two hydroxyl or epoxy groups, (ii) copolymers or copolymeric polyacids bearing carboxylic acid groups or anhydride groups and hydroxyl groups, and (iii) mixtures thereof, and 10 to 40 weight parts of one or more than one extender having an average particle size ranging from 0.5 μm or more and as high as 45 μm or less, preferably chosen from microcrystalline silica, diatomaceous silica, kaolin, bentonite, and anhydrous aluminosilicate clay delaminated. In the inventive binder compositions, the ratio of the wet over dry tensile strength of said composition is about 0.5 or greater. The present invention further provides products coated or impregnated with the binder, such as heat-resistant fiberglass nonwovens used for insulation. The aqueous binder may further comprise one or more phosphorous-containing accelerator.

FIELD OF THE INVENTION

The present invention relates to reduced cost, formaldehyde-free curable aqueous binder compositions containing extenders and yet retain their hot wet tensile strength properties when cured. More specifically, the present invention relates to compositions comprising from 10 to 40 weight % of one or more extender, based on the weight of one or more formaldehyde-free curable aqueous binder, wherein the ratio of the hot-wet tensile strength to the dry tensile strength of said composition, is about 0.5 or greater.

BACKGROUND OF THE INVENTION

Binders for heat-resistant non-woven materials, such as fiberglass insulation, have mostly contained resins, such as formaldehyde condensate resins that include urea-formaldehyde (UF) and phenol-formaldehyde (PF). These resins are inexpensive, however they steadily emit harmful formaldehyde gasses over their useful life. Further, such resins tend to yellow over time and can emit a foul odor when wet.

Recently, formaldehyde-free acrylic thermosetting binders have been introduced. Such aqueous acrylic resins, despite being odor-free and emitting virtually no formaldehyde have increased the cost of manufacturing fiberglass insulation or other fibrous products compared to costs associated with the use formaldehyde condensates.

U.S. Pat. No. 6,146,746, to Reck et al., discloses thermosettable aqueous binders comprising carboxylic acid functional polymers obtained by free-radical polymerization mixed with alkanolamines, which binders may contain auxiliaries such as aluminum silicates, pyrogenic silica, precipitated silica, fluorspar and heavy spar, talc, calcium carbonate and iron oxide. The binders allegedly provide good flexural modulus under hot and damp conditions. However, the auxiliaries mentioned can hamper the effectiveness of the binder or reduce the strength of the cured binder below acceptable levels. For example, pyrogenic silica, like any nanoparticle-size additive, can absorb binder, thereby masking its effectiveness. Calcium carbonate and iron oxide both interfere with the condensation reaction that cures the binder, and the carbonate also induces foaming and neutralizes the carboxylic acid functional polymer.

Accordingly, the present inventors have unexpectedly discovered formaldehyde-free aqueous binder compositions that are lower in cost than the prior formaldehyde-free binders and which provide good hot wet tensile strengths when cured and which do not suffer from the disadvantages discussed above.

SUMMARY OF THE INVENTION

According to the present invention, formaldehyde-free curable aqueous compositions comprise 100 weight parts of one or more than one binder chosen from (i) mixtures of one or more than one polycarboxylic acid or polymeric polyacid, each comprising at least two carboxylic acid groups, anhydride groups or salts thereof, and one or more than one polyol compound having a molecular weight of 1000 or less and comprising at least two hydroxyl or epoxy groups, (ii) one or more copolymer or copolymeric polyacid including, as copolymerized units, one or more monomer bearing carboxylic acid groups or anhydride groups and one or more hydroxyl group-bearing monomer, and (iii) mixtures of (i) and (ii), wherein, the said carboxylic acid groups, anhydride groups or salts thereof are neutralized to the extent of 35% or less with a fixed base, and, further wherein, in each of (i) and (ii), the ratio of the number of equivalents of the said carboxylic acid groups, anhydride groups or salts thereof to the number of equivalents of the said hydroxyl groups is from 1/0.01 to 1/3, the binder mixed with 10 to 40 weight parts of one or more than one extender having an average particle size ranging from 0.5 μm or more and as high as 45 μm or less chosen from microcrystalline silica, kaolin, diatomaceous silica, calcined aluminum silicate, wollastonite, calcium metasilicate, alkali aluminum silicate, anhydrous aluminosilicate clay delaminated, ground glass, nepheline syenite, hydrotalcite, mica, smectite, vermiculite, titanium dioxide, zinc oxide, and mixtures thereof.

In the inventive binder compositions, the ratio of the wet over dry tensile strength of said composition is about 0.5 or greater.

According to the present invention, a product coated or impregnated with the binder comprises heat-resistant nonwovens such as, for example, nonwovens composed of fiberglass or other heat-resistant fibers used for insulation. Binder coated or impregnated articles may comprise fibrous shaped articles, such as sheets or panels, wherein the articles may comprise heat-resistant fibers, such as glass fiber, natural fibers, such as cellulosics, hemp, sisal or animal fiber, or synthetic fibers, such as aramid or PVC fiber.

The aqueous binder may further comprise one or more phosphorous-containing accelerator. Additionally, the aqueous binder may further comprise one or more emulsion (co)polymer, one or more epoxy resin or other highly reactive polyol, or combinations thereof.

DETAILED DESCRIPTION OF THE INVENTION

This invention is directed to a low cost, formaldehyde-free curable aqueous binder compositions that comprise 10 wt. % or more, or 15 wt. % or more, and as much as 40 wt. %, or as much as 30 wt. %, based on binder solids, of an inorganic extender while maintaining the hot wet tensile strength and the performance of the cured binder, also referred to as “hot-wet retention”. Specifically, the ratio of the hot-wet tensile strength of the extender-containing binder composition of the present invention to the dry tensile strength of the same binder, when cured is about 0.5 or greater, preferably about 0.70 or greater, and, more preferably, about 0.8 or greater. Further, products coated or impregnated with the cured binder exhibit good “recovery”, which is defined as the relative thickness of a fiberglass insulation batt after compression.

The compositions of the present invention provide reduced-cost, formaldehyde free binders useful for coating and impregnating heat-resistant nonwovens, such as nonwovens composed of fiberglass, e.g. fiberglass insulation, or other fibrous substrates, such as sheets or ceiling panels.

In measuring the ratio of the hot-wet tensile strength of the cured extender-containing binder composition to the dry tensile strength of the same cured binder, the uncertainty may range as high as 0.05. Accordingly, such a measured ratio having a value of “about 0.5” may include actual ratios of from 0.45 to 0.55.

All ranges recited are inclusive and combinable. For example, an average particle size of 1.3 μm or more, for example, 1.5 μm or more, which may be 4.5 μm or less, or 4.0 μm or less, will include ranges of 1.3 μm or more to 4.5 μm or less, 1.5 μm or more to 4.5 μm or less, 1.5 μm or more to 4.3 μm or less, and 1.3 μm or more to 4.3 μm or less.

Unless otherwise indicated, all temperature and pressure units are standard temperature and pressure (STP).

All phrases comprising parenthesis denote either or both of the included parenthetical matter and its absence. For example, the phrase “(co)polymer” includes, in the alternative, polymer, copolymer and mixtures thereof.

As used herein, the phrase “wet over dry tensile strength” means a ratio of those two strengths when measured, as follows: Prepare a sample of binder-impregnated glass microfiber filter paper (20.3 cm×25.4 cm) by drawing it through a trough filled with 200 g of a pre-mixed binder solution that has been further mixed by agitation, sandwiching the soaked sample between two cardboard sheets to absorb excess binder, and pressing between the two cardboard sheets in a Birch Brothers Laboratory Patter set at a speed setting of 5 and at a pressure of 10 psi (68.9476 kPa). Dry the sample at 90° C. in a Mathis Oven that is vented or equipped with a devolatilizer for 90 seconds and, when dry, weigh it to determine a post-dry weight for calculating add-on. Cure the sample at 210° C. for 60 seconds in a Mathis Oven that is vented or equipped with a devolatilizer. Cut the cured coated sheets into 1 in×4 in (2.54 cm×10.16 cm) in size for tensile strength testing. Soak the cut cured coated sheets for 30 minutes at 85° C. just prior to wet tensile strength testing. Test tensile strength of each of the wet and dry samples in the machine direction in a Thwing-Albert Intelect 500 tensile tester, having a fixture gap set at 2 inches (5.08 cm) and a pull rate set at 2 inches/minute (5.08 cm/minute). Record each tensile strength as the peak force measured during parting or breaking each tested strip in two. Finally, divide wet tensile strength by dry tensile strength to calculate a ratio of the wet tensile strength to the dry tensile strength.

As used herein, the phrase “addition polymer” refers to any (co)polymer that comprises ethylenically unsaturated monomers as (co)polymerized units, such as the polymeric polyacid and the copolymer.

As used herein, the phrase “aqueous” includes water and mixtures composed substantially of water and water-miscible solvents.

As used herein, the phrase “average particle size”, refers to particle diameter or the largest dimension of a particle this can be determined by laser light scattering or by a sedimentation method using a hygrometer or other suitable means. In the sedimentation method, the reported average particle size “x” denotes the point on the particle size distribution curve at which 50% by weight of the measured batch of particles is finer than than “x”.

As used herein, unless otherwise indicated, the phrase “copolymer” includes, independently, copolymers, terpolymers, block copolymers, segmented copolymers, graft copolymers, and any mixture or combination thereof.

As used herein, the phrase “delaminated” and “exfoliated” clay refer to layered silicates in which the layers have been separated from each other.

As used herein, unless otherwise indicated, the phrase “melt viscosity” refers to the melt viscosity of a polymer or resin, as measured in centipoises at 150° C. using a Brookfield Viscometer in accordance with the manufacturer or equipment supplier's recommendations.

As used herein, the term “maleic” comprises either maleic acid or maleic anhydride independently of each other, unless otherwise indicated.

As used herein, the term “(meth)acrylate” means acrylate, methacrylate, and mixtures thereof and the term “(meth)acrylic” used herein means acrylic, methacrylic, and mixtures thereof.

As used herein, unless otherwise indicated, the phrase “molecular weight” refers to the weight average molecular weight of a polymer as measured by gel permeation chromatography.

As used herein, the phrase “wt. %” stands for weight percent.

The extenders useful in the present invention have an average particle size, as determined by laser light scattering, of 0.5 μm or more, or 5 μm or more and as high as 45 μm or less, or 35 μm or less. Extenders having more than 50 wt. % of fines less than 1 μm in diameter provide an excessive surface area and absorb in the surface of the substrate, effectively preventing the binder from sticking to the substrate. Extenders having an average particle size of more than 45 μm interfere with the continuous interface between binder and substrate. Preferably, extenders are screened prior to use in a screen which limits their particle size to an acceptable range. Suitable screens have a grid size ranging from 0.5 μm to 45 μm, or from 12,700 mesh to 325 mesh, that is, they allow particles having a size of from 1 μm to 45 μm to pass through them. More preferably, suitable extenders will pass through a screen having a 45 μm grid size but would not pass through a screen having a 0.5 μm grid size or a filter having a 0.5 μm lower resolution limit. Thus, extenders may be screened by passing them through a 45 μm and onto a grid plate, screen or filter having a 0.5 μm grid size or lower resolution limit.

Suitable extenders should not react with the binder or interfere with the curing of the binder. For this reason, the extenders of the present invention are not iron leachable, and do not foam or react in the presence of carboxylic acid. Accordingly, suitable extenders do not contain iron, sulfate, phosphate or carbonate groups. In addition, suitable extenders may be calcined to minimize their ability to absorb binder. Such extenders may include calcined clay and calcined silicates, such as calcined aluminum silicates.

Suitable extenders may be chosen from microcrystalline silica, kaolin, bentonite, calcined aluminum silicate, wollastonite, calcium metasilicate, alkali aluminum silicate, diatomaceous silica, ground glass, nepheline syenite, hydrotalcite, mica, smectite, vermiculite, anhydrous aluminosilicate clay delaminated, titanium dioxide, zinc oxide, and mixtures thereof. Smectite includes the layered clays and phyllosilicates, such as montmorillonite, bentonite, saponite, beidellite, montronite, hectorite, and stevensite. Kaolin clay, smectites or phyllosilicates may or may not be surface treated to render them hydrophobic, such as with trialkylarylammonium compounds.

Preferred extenders may comprise microcrystalline silica, diatomaceous silica, bentonite and kaolin clays, anhydrous aluminosilicate delaminated, or their mixtures. Microcrystalline silica comes in several forms, including cristobalite or christobalite and tridymite.

Binder compositions may comprise one or more mixtures of one or more than one polycarboxylic acid or polymeric polyacid, each comprising at least two carboxylic acid groups, anhydride groups or salts thereof, and one or more than one polyol compound having a molecular weight of 1000 or less and comprising at least two hydroxyl groups and, optionally, a phosphorous-containing accelerator, wherein the ratio of the number of equivalents of said carboxylic acid groups, anhydride groups, or salts thereof to the number of equivalents of said hydroxyl groups is from 1/0.01 to 1/3, and wherein the carboxyl groups are neutralized to an extent of less than 35% with a fixed base.

Alternatively, binders may comprise one or more rapidly curing copolymer or copolymeric polyacid including, as copolymerized units, one or more monomer bearing carboxylic acid units and one or more hydroxyl group-bearing monomer, wherein the ratio of the number of equivalents of the said carboxylic acid groups, anhydride groups or salts thereof to the number of equivalents of the said hydroxyl groups is from 1/0.01 to 1/3, and, further wherein, the said carboxylic acid groups, anhydride groups or salts thereof are neutralized to the extent of 35% or less with a fixed base.

The formaldehyde-free curable aqueous composition is substantially thermoplastic, or substantially uncrosslinked, when it is applied to the substrate, although low levels of deliberate or adventitious crosslinking may be present. On heating the binder, the binder is dried and curing is effected, either sequentially or concurrently. By “curing” is meant herein a structural or morphological change which is sufficient to alter the properties of a flexible, porous substrate to which an effective amount of polymeric binder has been applied such as, for example, covalent chemical reaction, ionic interaction or clustering, improved adhesion to the substrate, phase transformation or inversion, hydrogen bonding, and the like.

This invention is directed to a formaldehyde-free curable aqueous composition. By “formaldehyde-free composition” herein is meant that the composition is substantially free from formaldehyde, and does not liberate substantial formaldehyde as a result of drying and/or curing. To minimize the formaldehyde content of the waterborne composition it is preferred, when preparing a polymer-containing formaldehyde-free curable aqueous composition, to use polymerization adjuncts such as, for example, initiators, reducing agents, chain transfer agents, biocides, surfactants, and the like, which are themselves free from formaldehyde, do not generate formaldehyde during the polymerization process, and do not generate or emit formaldehyde during the treatment of the treatment of one or more substrates. By “substantially free from formaldehyde” herein is meant that when low levels, e.g. less than 2.0 wt. %, preferably less than 0.1 wt. %, more preferably less than 0.0001 wt. %, and most preferably less than 100 ppb of formaldehyde are acceptable in the waterborne composition or when compelling reasons exist for using adjuncts which generate or emit formaldehyde, substantially formaldehyde-free waterborne compositions may be used.

Suitable polycarboxylic acids should be sufficiently nonvolatile that they will remain available for reaction with the polyol in the composition during heating and curing operations. The polyacid may be one or more compound having a molecular (formula) weight less than 1000 bearing at least two carboxylic acid groups, anhydride groups, or salts thereof such as, for example, citric acid, butane tricarboxylic acid, and cyclobutane tetracarboxylic acid.

Suitable polymeric polyacids may include, for example, one or more polyesters containing at least two carboxylic acid groups, or addition polymers or oligomers containing at least two copolymerized carboxylic acid or carboxylic anhydride functional monomers. The polymeric polyacid may preferably be one or more addition polymer formed from at least one ethylenically unsaturated monomer. The addition polymer may be in the form of a solution of the addition polymer in an aqueous medium including, for example, one or more alkali-soluble resin which has been solubilized in a basic medium, may be in the form of an aqueous dispersion such as, for example, an emulsion-polymerized dispersion, or may be or in the form of an aqueous suspension.

The copolymer including, as copolymerized units, one or more monomer bearing carboxylic acid units and one or more hydroxyl group-bearing monomer (hereinafter “the copolymer”), may be the polymerization reaction product of one or more ethylenically unsaturated carboxylic acids and one or more hydroxyl-group containing ethylenically unsaturated comonomer.

Each of the (co)polymeric polyacid and the copolymer contain at least two carboxylic acid groups, anhydride groups, or salts thereof. Units that may be copolymerized therein include ethylenically unsaturated carboxylic acids such as, for example, methacrylic acid, acrylic acid, crotonic acid, fumaric acid, maleic acid, 2-methyl maleic acid, itaconic acid, citraconic acid, mesaconic acid, 2-methyl itaconic acid, cyclohexenedicarboxylic acid, α,β-methylene glutaric acid, monoalkyl maleates, and monoalkyl fumarates; ethylenically unsaturated anhydrides such as, for example, maleic anhydride, itaconic anhydride, citraconic anhydride, mesaconic anhydride, acrylic anhydride, and methacrylic anhydride; and salts thereof. Such monomers should be used in the copolymer or the copolymeric polyacid in amounts that provide acid copolymerized units in the amount of from 1 to 100 wt. %, based on the weight of the addition polymer. In the copolymer, such monomers should be used in amounts that provide acid copolymerized units at a level of from 1 to 99 wt. %, more preferably at a level of from 10 to 90 wt. %, based on the weight of the copolymer. The remainder of the copolymer or copolymeric polyacid (aside from copolymerized acid group-containing units) may comprise hydroxyl group containing copolymerized units, and, optionally, copolymerized units of additional ethylenically unsaturated monomers. Accordingly, the copolymer and the copolymeric polyacid may comprise, as copolymerized units, hydroxyl group containing ethylenically unsaturated monomers, and, optionally, as copolymerized units, additional ethylenically unsaturated monomers.

The at least one copolymerized hydroxyl containing monomer in the copolymer of the present invention may comprise one or more hydroxyl group-including monomer of Formula I, CH2=C(R1)CH(R2)OR3  (I) wherein R1 and R2 are independently selected from hydrogen, methyl, and —CH2OH; and R3 is selected from hydrogen, —CH2CH(CH3)OH, —CH2CH2OH, C(CH2OH)2—C2H5, and (C3-C12) polyol residues; or of Formula

-   -   wherein R is selected from CH3, Cl, Br, and C6H5; and R1 is         selected from H, OH, CH2OH, CH(CH3)OH, glycidyl, CH(OH)CH2OH,         and (C3-C12)polyol residues; preferably at a level of from 1% to         99%, more preferably at a level of from 10% to 90% by weight,         based on the weight of the polymer. Preferred hydroxyl         group-containing monomers are allyl alcohol and         3-allyloxy-1,2-propanediol. Monomers of Formula I and Formula II         can be prepared by a variety of synthetic routes known to those         skilled the art. For example, allyl chloride can be reacted with         various polyhydroxy compounds to give, for example, the         corresponding allyloxy derivatives of sugars, glycerine,         erythritol, trimethylolpropane (CAS# 77-99-6) and         pentaerythritol. Alternatively, allyl alcohol can be reacted         with various halomethyl derivatives, especially chloromethyl         compounds, to prepare allyloxy derivatives; for example, the         reaction of allyl alcohol with epichlorohydrin would produce         3-allyloxy-1,2-propanediol. Vinyl glycols, such as         1-butene-3,4-diol, for example, can be prepared by methods such         as those described in U.S. Pat. No. 5,336,815. Allyloxy         compounds that would hydrolyze to allyloxy compounds of Formula         I under the conditions of aqueous polymerization, for example         allyl glycidylether, are also useful as monomers to produce         polymer additives of the present invention.

The (C₃-C₁₂)-containing polyols useful to prepare allyloxy compounds of Formula I include, for example, (C₃-C₆)-polyhydroxy compounds such as erythritol, pentaerythritol and glycerine; and sugar alcohols such as xylitol, sorbitol and mannitol. Additional suitable (C₃-C₁₂)-containing polyols include, for example, polyhydroxy aldehyde and ketone sugars such as glucose, fructose, galactose, maltose, sucrose, lactose, erythrose and threose. Examples of suitable unsaturated non-ionizable monomers include allyl alcohol, methallyl alcohol, allyloxyethanol, allyloxypropanol, 3-allyloxy-1,2-propanediol, trimethylolpropane allyl ether, allyloxy(sugars), such as allyloxy(glucose), allyloxy(fructose) and allyloxy(mannose), erythritol monoallyl ether, pentaerythritol monoallyl ether, and 1-butene-3,4-diol. The prefixes “(C₃-C₁₂)-” and “(C₃-C₆)-,” as used herein, refer to organic compounds or structural portions of organic compounds containing 3 to 12 carbon atoms and 3 to 6 carbon atoms, respectively. The terms “polyol” and “polyhydroxy,” as used herein, refer to organic compounds or structural portions of organic compounds containing two or more hydroxy groups.

Useful additional ethylenically unsaturated monomers may be included as copolymerized units in each of the copolymeric polyacid and the copolymer. Such monomers may include acrylic ester monomers including methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, butyl methacrylate, isodecyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate; acrylamide or substituted acrylamides; styrene or substituted styrenes; butadiene; vinyl acetate or other vinyl esters; acrylonitrile or methacrylonitrile; and the like.

In an embodiment of the present invention, the copolymeric polyacid or the copolymer has improved water resistance and further comprises as copolymerized units one or more ethylenically unsaturated monomer having a solubility of less than 2 g/100 g of water at 25° C. in the amount of 3 or more wt. %, and as much as 25 wt. % or less, or 20 wt. % or less, or 15 wt. % or less, based on the total weight of monomers used to make the curable aqueous binder composition. The ethylenically unsaturated monomer may be chosen from ethyl (meth)acrylate, methyl methacrylate, butyl (meth)acrylate, styrene, mono-alkyl (meth)acrylamide, and di-alkyl (meth)acrylamide. Still further, the copolymeric polyacid or the copolymer may comprise, as copolymerised units, one or more polyacid homopolymer.

The preferred amount of each of the ethylenically unsaturated monomers varies depending on the monomer used. In general, it is preferred to use from 3 to 15 wt. %, based on the total weight of monomers in the curable aqueous binder composition, of ethylenically unsaturated monomer having a solubility in water of less than 1 g/100 g water at 25° C. Further, it is preferred to use from 10 to 25 wt. %, based on the total weight of monomers in the curable aqueous binder composition, of ethylenically unsaturated monomers having a solubility in water of from 1 g/100 g to 2 g/100 g water at 25° C. Specifically, it is preferred to use from 10 to 25 wt. % ethyl (meth)acrylate, from 10 to 20 wt. % methyl methacrylate, from 3 to 15 wt. % butyl (meth)acrylate, from 3 to 10 wt. % styrene, from 3 to 8 wt. % t-octyl acrylamide, and from 5 to 15 wt. % t-butyl acrylamide, based on the total weight of monomers in the curable aqueous binder composition.

The (co)polymeric polyacid and the copolymer each may have a weight average molecular weight, as measured by gel permeation chromatography (GPC), of from 300 to 10,000,000. Preferred is a molecular weight of 500 or more, more preferably 1000 or more, and the preferred molecular weight may range as high as 250,000, more preferably it may range up to 20,000. When the (co)polymeric polyacid is one or more alkali-soluble resin having a carboxylic acid, anhydride, or salt thereof, in the amount of from 5 to 30 wt %, based on the total weight of the (co)polymeric polyacid, a molecular weight from 5,000 to 100,000 is preferred. Higher molecular weight alkali-soluble resins can lead to curable compositions which exhibit excessive viscosity. When the copolymer is one or more alkali-soluble resin having a carboxylic acid, anhydride, or salt thereof, in the amount of from 5 to 50 wt %, based on the total weight of the copolymer, a molecular weight from 5,000 to 100,000 is preferred because higher molecular weight alkali-soluble copolymers can lead to curable compositions which exhibit excessive viscosity.

When the addition polymer is in the form of an aqueous dispersion or an aqueous suspension and low levels of precrosslinking or gel content are desired, low levels of multi-ethylenically unsaturated monomers such as, for example, allyl methacrylate, diallyl phthalate, 1,4-butylene glycol dimethacrylate, 1,6-hexanedioldiacrylate, and the like, may be used at a level of from 0.01% to 5%, by weight based on the weight of the acrylic emulsion copolymer.

When the addition polymer is in the form of an aqueous dispersion the diameter of the addition polymer particles may be from 80 nanometers to 1000 nanometers, as measured using a Brookhaven BI-90 Particle Sizer, which employs a light scattering technique. However, polymodal particle size distributions such as those disclosed in U.S. Pat. Nos. 4,384,056 and 4,539,361, hereby incorporated herein by reference, may be employed.

When the addition polymer is in the form of an aqueous dispersion the addition polymer particles may be made up of two or more mutually incompatible copolymers. These mutually incompatible copolymers may be present in various morphologies, for example, core/shell particles, core/shell particles with shell phases incompletely encapsulating the core, core/shell particles with a multiplicity of cores, interpenetrating network particles, and the like.

The addition polymer may be prepared by solution polymerization, emulsion polymerization, or suspension polymerization techniques for polymerizing ethylenically-unsaturated monomers which are well known in the art. When it is desired to use emulsion polymerization, anionic or nonionic surfactants, or mixtures thereof, may be used. The polymerization may be carried out by various means such as, for example, with all of the monomer in the reaction kettle at the beginning of the polymerization reaction, with a portion of the monomer in emulsified form present in the reaction kettle at the beginning of the polymerization reaction, and with a small particle size emulsion polymer seed present in the reaction kettle at the beginning of the polymerization reaction.

The polymerization reaction to prepare the addition polymer may be initiated by various methods known in the art such as, for example, by using the thermal decomposition of an initiator and by using an oxidation-reduction reaction (“redox reaction”) to generate free radicals to effect the polymerization. In another embodiment the addition polymer may be formed in the presence of phosphorous-containing chain transfer agents such as, for example, hypophosphorous acid and its salts, as is disclosed in U.S. Pat. No. 5,294,686, which is hereby incorporated herein by reference, so as to incorporate the phosphorous-containing accelerator and the polyacid component in the same molecule. The polymer can be prepared in solvent/water mixtures such as, for example, i-propanol/water, tetrahydrofuran/water, and dioxane/water.

Chain transfer agents such as mercaptans, polymercaptans, and halogen compounds may be used in the polymerization mixture to moderate the molecular weight of the acrylic emulsion copolymer. Generally, from 0% to 1% by weight, based on the weight of the polymeric binder, of C₄-C₂₀ alkyl mercaptans, mercaptopropionic acid, or esters of mercaptopropionic acid, may be used.

The carboxylic acid groups, anhydride groups, or the salts thereof in the polyacid component, polymeric polyacid or copolymer of the formaldehyde-free curable aqueous composition are neutralized with fixed base to an extent of less than 35%, calculated on an equivalents basis. The term “neutralization”, as used herein, means contacting the polyacid component, polymeric polyacid or copolymer with one or more fixed base before, during, or after the preparation of the curable aqueous composition. Neutralization should, if it is desired, be performed prior to treating a fibrous, e.g. nonwoven, substrate. Preferably, less than 20% of the carboxylic acid groups, calculated on an equivalents basis, are neutralized with a fixed base. More preferably, less than 5% of the carboxylic acid groups, calculated on an equivalents basis, are neutralized with a fixed base. When the half ester of a dicarboxylic acid or the anhydride of a dicarboxylic acid is used, the equivalents of acid are calculated to be equal to those of the corresponding dicarboxylic acid.

“Fixed base”, or “permanent base”, as used herein, refers to a monovalent base which is sufficiently nonvolatile that it will remain non-volatile under the conditions of the neutralization treatment. Such bases may include, for example, sodium hydroxide, potassium hydroxide, sodium carbonate, or t-butylammonium hydroxide. Volatile bases such as, for example, ammonia or volatile lower alkyl amines, do not function as the fixed base of this invention and do not contribute to the required degree of neutralization by a fixed base, but may be used in addition to the fixed base. Fixed multivalent bases such as, for example, calcium carbonate may tend to destabilize an aqueous dispersion, if the addition polymer is used in the form of an aqueous dispersion, but may be used in minor amount.

When the formaldehyde-free aqueous composition comprises one or more polyacids or polymeric polyacids not having hydroxyl group containing monomers as copolymerized units, the compositions further contain one or more polyol containing at least two hydroxyl groups. The polyol should be sufficiently nonvolatile that it will substantially remain available for reaction with the polyacid in the composition during heating and curing. The polyol may be one or more compound with a molecular weight of less than 1000 bearing at least two hydroxyl groups. Suitable polyols include, for example, ethylene glycol, glycerol, pentaerythritol, trimethylol propane, sorbitol, sucrose, glucose, resorcinol, catechol, pyrogallol, glycollated ureas, 1,4-cyclohexane diol, diethanolamine, triethanolamine, dipropanolamine, diisopropanolamine, triisopropanolamine, methyldiethanolamine, butyldiethanolamine and methyldiisopropanolamine and certain reactive polyols such as, for example, β-hydroxyalkylamides such as, for example, bis-[N,N-di(β-hydroxyethyl)]adipamide, as may be prepared according to the teachings of U.S. Pat. No. 4,076,917, hereby incorporated herein by reference, or may include one or more addition polymer containing at least two hydroxyl groups or active hydrogen groups, such as, for example, polyvinyl alcohol, partially hydrolyzed polyvinyl acetate, and addition homopolymers or copolymers of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, dialkylaminoalkyl (meth)acrylamide, and the like.

The ratio of the number of equivalents of carboxy, anhydride, or salts thereof in the curable aqueous binder composition, i.e. of the polyacid, (co)polymeric polyacid or copolymer, to the number of equivalents in the curable aqueous binder composition, i.e. of hydroxyl in the polyol, or the hydroxyl-group containing comonomer, or the copolymeric polyacid or copolymer containing hydroxyl groups, ranges from 1/0.01 to 1/3. An excess of equivalents of carboxy, anhydride, or salts thereof of the polyacids, polymeric polyacid or copolymer to the equivalents of hydroxyl in the polyol, polymeric polyacid or copolymer is preferred. More preferably, the ratio of the number of equivalents of carboxy, anhydride, or salts thereof in the in the curable aqueous binder composition to the number of equivalents of hydroxyl in the curable aqueous binder composition ranges from 1/0.2 to 1/1. The most preferred ratio of the number of equivalents of carboxy, anhydride, or salts thereof in the polyacids, polymeric polyacid or copolymer or their mixtures to the number of equivalents of hydroxyl in the polyol, polymeric polyacid or copolymer or their mixtures ranges from 1/0.2 to 1/0.8.

In certain embodiments, the curable composition can include one or more phosphorous-containing accelerator which can include phosphorous-containing compounds such as, for example, alkali metal hypophosphite salts, alkali metal phosphites, alkali metal polyphosphates, alkali metal dihydrogen phosphates, polyphosphoric acids, and alkyl phosphinic acids or can include oligomers or polymers bearing phosphorous-containing groups such as, for example, addition polymers of acrylic and/or maleic acid formed in the presence of sodium hypophosphite, or the polymeric polyacid or copolymer of the present invention prepared from ethylenically unsaturated monomers in the presence of phosphorous salt chain transfer agents or terminators, or addition polymers containing acid-functional monomer residues such as, for example, copolymerized phosphoethyl methacrylate, and like phosphonic acid esters, and copolymerized vinyl sulfonic acid monomers, and their salts. The phosphorous-containing species can be used at a level of from 0% to 40%, preferably from 0% to 5%, further preferably from 0% to 2.5%, more preferably from 0% to 1%, and further more preferably from 0% to 0.5% by weight based on the weight of the polymer of the present invention.

In one embodiment of the invention, the formaldehyde-free curable aqueous composition may contain a highly reactive polyol without, or in addition to, the phosphorous-containing accelerator. The highly reactive polyol may be mixed with polyacids or polyacid (co)polymers or copolymers or may be part of the polyacid (co)polymers or copolymers. The composition preferably includes a highly reactive polyol such as, for example, a α-hydroxyalkylamide of the formula: [HO(R³)₂C(R²)₂C—N(R¹)—C(O)—]_(n)-A-[—C(O)—N(R¹)—C(R²)₂C(R³)₂OH]n′  (I)

-   -   wherein A is a bond, hydrogen or a monovalent or polyvalent         organic radical derived from a saturated or unsaturated alkyl         radical wherein the alkyl radical contains from 1-60 carbon         atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl,         heptyl, octyl, nonyl, decyl, eicosyl, triacontyl, tetracontyl,         pentacontyl, hexylcontyl and the like; aryl, for example, mono         and dinuclear aryl such as phenyl, naphthyl and the like;         tri-lower alkyleneamino such as trimethyleneamino,         triethyleneamino and the like; or an unsaturated radical         containing one or more ethylenic groups         such as ethenyl, 1-methylethenyl, 3-butenyl-1,3-diyl,         2-propenyl-1,2-diyl, carboxy lower alkenyl, such as         3-carboxy-2-propenyl and the like, lower alkenyl carbonyl         alkenyl such as 3-methoxycarbonyl-2-propenyl and the like; R¹ is         hydrogen, lower alkyl of from 1-5 carbon atoms such as methyl,         ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, pentyl and the         like or hydroxy lower alkyl of from 1-5 carbon atoms such as         hydroxyethyl, 3hydroxypropyl, 2-hydroxypropyl, 4-hydroxybutyl,         3-hydroxybutyl, 2hydroxy-2-methylpropyl, 5-hydroxypentyl,         4-hydroxypentyl, 3hydroxypentyl, 2-hydroxypentyl and the isomers         of pentyl; R² and R³ are the same or different radicals selected         from hydrogen, straight or branched chain lower alkyl of from         1-5 carbon atoms or one of the R² and one of the R³ radicals may         be joined to form, together with the carbon atoms, such as         cyclopentenyl, cyclohexyl and the like; n is an integer having a         value of 1 or 2 and n′ is an integer having a value of 0 to 2 or         when n′ is 0, a polymer or copolymer (i.e., n has a value         greater than 1 preferably 2-10) formed from the         β-hydroxyalkylamide when A is an unsaturated radical. Preferred         reactive polyols are those of the foregoing Formula (I), wherein         R¹ is H, lower alkyl, or HO(R³)₂C(R²)₂C—, n and n′ are each 1,         -A- is —(CH₂)_(m) is 0-8, preferably 2-8, each case is H and the         other is H or a C₁-C₅ alkyl; for example,         HO—CH(R³)CH₂—N(R¹)—C(O)—(CH₂)_(m)—C(O)—N(R¹)—CH₂CH(R³)OH  (Ia)     -   wherein R¹, R³, and m have the meanings just given. Examples of         the most preferred reactive polyols fall within the formula:         (HO—CH(R³)CH₂)₂N—C(O)—(CH₂)_(m)—C(O)—N(CH₂CH(R³)OH)₂  (Ib)     -   wherein R³ is limited to H in both cases or —CH₃ in both cases.         Specific examples falling within Formula Ib are         bis[N,N-di(β-hydroxyethyl)]adipamide,         bis[N,N-di(β-hydroxypropyl)]azelamide,         bis[N-N-di(β-hydroxypropyl)]adipamide,         bis[N-N-di(β-hydroxypropyl)]glutaramide,         bis[N-N-di(β-hydroxypropyl)]succinamide, and         bis[N-methyl-N-(β-hydroxyethyl)]oxamide.

Other suitable highly reactive polyols include epoxy resins or bisphenol epoxy resins, such as bisphenol A or bisphenol F epoxy diglycidyl or polyglycidyl ethers, polyglycidyl esters, polyglycidyl amines, multifunctional epoxy resins having two or more epoxy or glycidyl groups, including polyol polyglycidyl ethers, such as butanediol diglycidyl ethers, neopentyl glycol diglycidyl ethers, pentaerythritol triglycidyl ethers, hexanediol diglycidyl ethers, phenol and cresol novolaks and resoles, and cycloaliphatic polyol diglycidyl ethers, such as tetrahydrophthalic acid diglycidyl ether, and 3,4-epoxycyclohexanecarboxylic acid-3′,4′ epoxycyclohexylmethyl ester.

In another embodiment the salts of the carboxyl groups are salts of functional alkanolamines with at least two hydroxyl groups such as, for example, diethanolamine, triethanolamine, dipropanolamine, and diisopropanolamine.

In yet another embodiment, the polyol and the phosphorous-containing accelerator may be present in the same addition polymer. In yet another embodiment the polymeric polyacids or copolymer, the polyol, and the phosphorous-containing accelerator may be present in the same addition polymer. As disclosed above, the carboxyl groups of the polyacid may be neutralized to an extent of less than 35% with a fixed base before, during, or after the mixing to provide the aqueous composition. Neutralization may be partially or wholly effected during the formation of the polyacid.

In yet still another embodiment, a higher level of water proofing of substrates may be achieved by adding one or more emulsion polymer including, as copolymerized units, greater than 30 wt. %, preferably greater than 40 wt. %, more preferably greater than 50 wt. %, and even more preferably greater than 60 wt. %, based on the weight of the emulsion polymer solids, of an ethylenically unsaturated acrylic monomer including a C₅ or greater alkyl group. By “emulsion polymer” herein is meant one or more polymer dispersed in aqueous media that has been prepared by emulsion polymerization. By “acrylic monomer including a C₅ or greater alkyl group” herein is meant one or more acrylic monomer bearing an aliphatic alkyl group having five or more C atoms, the alkyl group including n-alkyl, s-alkyl, i-alkyl, and t-alkyl groups. Suitable ethylenically unsaturated monomers including a C₅ or greater alkyl group include (C₅-C₃₀) alkyl esters of (meth)acrylic acid, such as amyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate; unsaturated vinyl esters of (meth)acrylic acid such as those derived from fatty acids and fatty alcohols; surfactant monomers including long chain alkoxy- or alkylphenoxy(polyalkylene oxide) (meth)acrylates, such as C₁₈H₃₇-(ethylene oxide)₂₀ methacrylate and C₁₂H₂₅-(ethylene oxide)₂₃ methacrylate; N-alkyl substituted (meth)acrylamides such as octyl acrylamide; and the like. The monomer including a C₅ or greater alkyl group can also contain functionality, such as amido, aldehyde, ureido, polyether and the like, but preferably does not contain an acid or hydroxy group. Emulsion polymers containing such monomers can be prepared by emulsion polymerization, preferably by the method for forming polymers of U.S. Pat. No. 5,521,266.

The emulsion polymer can also include, as copolymerized units, from 0 to 10 wt. %, preferably from 0 to 5 wt. %, based on the weight of the emulsion polymer solids, monomer bearing a carboxylic acid group, anhydride group, or salt thereof or hydroxyl-group, such as (meth)acrylic acid and hydroxyethyl (meth)acrylate.

The emulsion polymer is present in an amount of from 1 to 10 wt. %, preferably from 1.5 to 5 wt. %, by weight based on the sum of the weight of the polyacid and the weight of the polyol, all weights being taken on a solids basis.

The curable composition can contain, in addition, conventional treatment components such as, for example, emulsifiers, pigments, fillers, anti-migration aids, curing agents, coalescents, surfactants, particularly nonionic surfactants, biocides, plasticizers, organosilanes, such as alkoxy silanes, like aminopropyltri(m)ethoxy silane or glycidylpropyltri(m)ethoxy silane, anti-foaming agents, corrosion inhibitors, particularly corrosion inhibitors effective at pH<4 such as thioureas, oxalates, and chromates, colorants, waxes, polyols which are not polymers of the present invention such as glycerol, alkanolamines, and polypropyleneglycol, other polymers not of the present invention, and anti-oxidants. However, the total amount of filler plus extender should not exceed 40% because the cured composition that results will not retain acceptable hot wet tensile strength.

The formaldehyde-free curable aqueous composition may be prepared by admixing water or aqueous carrier with copolymer or copolymeric polyacid, or with the polyacid or polymeric polyacid and the polyol, or mixtures thereof, and, if desired, the phosphorous-containing accelerator using conventional mixing techniques. Where one or more emulsion is added, the curable aqueous composition may be formed by adding the emulsion polymer to the mixture of the copolymer, polyacid and the polyol, copolymeric polyacid, or polymeric polyacid and polyol, or mixtures thereof, which mixture may be at a pH of from 2.0 to 4.5. Agglomeration of the emulsion polymer under these conditions can occur if the emulsion polymer is not sufficiently stable; agglomeration is believed to be undesirable for processing and efficiency reasons. To achieve stability under these conditions in some embodiments it is optionally preferred to add one or more surfactant to the emulsion polymer before or during the addition of the emulsion polymer to the mixture of the copolymer, (co)polymeric polyacid, and/or polyacid and polyol. Preferred is the addition of from 0.5% to 20%, preferably from 2% to 10%, by weight, based on the weight of emulsion polymer solids. Preferred is one or more surfactant having a HLB value of greater than 15.

In one aspect of the present invention a method for treating one or more substrate is provided. Such treatments can be commonly described as, for example, coating one or more substrate, sizing one or more substrate, saturating one or more substrate, bonding one or more substrate, and the like. Typical substrates include wood such as wood particles, fibers, chips, flour, pulp, and flakes; metal; plastic; fibers; woven and nonwoven fabrics; paper oil- and air-filter stock, rayon nonwoven wipes, polyester/cotton woven fabrics, cellulosic laminating stock, nonwoven cellulosic felts, and wood fibers and flakes consolidated into or suitable to be consolidated into fiberboard, hardboard, particleboard, oriented strand board, and the like.

The curable composition can be applied to a substrate by conventional techniques such as, for example, air or airless spraying, padding, saturating, roll coating, curtain coating, beater deposition, coagulation, or the like.

In one embodiment of this invention the curable composition can be used as a binder for heat-resistant nonwoven fabrics such as, for example, nonwovens which contain heat-resistant fibers such as, for example, aramid fibers, ceramic fibers, metal fibers, carbon fibers, polyimide fibers, certain polyester fibers, rayon fibers, rock wool, and glass fibers. By “heat-resistant fibers” herein is meant fibers which are substantially unaffected by exposure to temperatures above 125° C. Heat-resistant nonwovens can also contain fibers which are not in themselves heat-resistant such as, for example, certain polyester fibers, rayon fibers, nylon fibers, and superabsorbent fibers, in so far as they do not materially adversely affect the performance of the substrate.

Nonwoven fabrics are composed of fibers which can be consolidated by purely mechanical means such as, for example, by entanglement caused by needle-punching, by an air-laid process, and by a wet-laid process; by chemical means such as, for example, treatment with a polymeric binder; or by a combination of mechanical and chemical means before, during, or after nonwoven fabric formation. Some nonwoven fabrics are used at temperatures substantially higher than ambient temperature such as, for example, glass fiber-containing nonwoven fabrics which are impregnated with a hot asphaltic composition pursuant to making roofing shingles or roll roofing material. When a nonwoven fabric is contacted with a hot asphaltic composition at temperatures of from 150° C. to 250° C., the nonwoven fabric can sag, shrink, or otherwise become distorted. Therefore, nonwoven fabrics which incorporate a curable composition should substantially retain the properties contributed by the cured aqueous composition such as, for example, tensile strength. In addition, the cured composition should not substantially detract from essential nonwoven fabric characteristics, as would be the case, for example, if the cured composition were too rigid or brittle or became sticky under processing conditions.

Heat treatment at from 120° C. to 400° C. for a period of time from 3 seconds to 15 minutes may be carried out; treatment at 150° C. to 225° C. is preferred, and, when using the phosphorous containing accelerator or reactive polyol, heat treatment at 150° C. to 200° C. is preferred. The drying and curing functions may be effected in two or more distinct steps, if desired. For example, the composition may be first heated at a temperature and for a time sufficient to substantially dry but not to substantially cure the composition and then heated for a second time at a higher temperature and/or for a longer period of time to effect curing. Such a procedure, referred to as “B-staging”, may be used to provide binder-treated nonwoven, for example, in roll form, which may at a later stage be cured, with or without forming or molding into a particular configuration, concurrent with the curing process.

The heat-resistant nonwovens may be used for applications such as, for example, insulation batts or rolls, as reinforcing mats for roofing or flooring applications, as roving, as microglass-based substrates for printed circuit boards or battery separators, as filter stock, as tape stock, and as reinforcement scrim in cementitious and non-cementitious coatings for masonry.

The treated cellulosic substrates may be used for applications such as, for example, laminates, industrial wipes, durable-press clothing, and oil and air filters, and consolidated wood products.

Nonwoven cellulosic wipes are beneficially strengthened under dry, water-wet and solvent-wet conditions which may be met in their use.

Oil- and air-filter stock is beneficially strengthened to give the composite integrity at high temperatures, and in the case of oil-filter applications, when saturated with hot oil.

The following examples are intended to illustrate the curable composition and the use thereof in the method for treating substrates.

EXAMPLES

Treatment of Glass Microfiber Filter Paper and Tensile Testing of Treated Substrate

Aqueous curable compositions were prepared with various amounts of a commercially available acrylic thermoset TSET™ No. 1, a mixture of poly(acrylic acid), triethanolamine and sodium hypophosphite, available from Rohm and Haas Company, Philadelphia, Pa. (53 wt. % solids in water, mfg. in U.S.A. between March, 2002 and March, 2004) mixed with extender. The comparative binder comprised a commercially available ACRONAL™ 2438 acrylic-maleic copolymer thermoset, available from BASF Aktiengesellschaft, Ludwigshafen, Germany (obtained June, 2002). The pH of the aqueous binder dispersions or solutions was adjusted to pH 3 with sulfuric acid and the solutions or dispersions were diluted to 200 g. with water providing a weight 5% solids mixture (Table 1). Glass microfiber filter paper sheets, GF/A (glass type A), (20.3×25.4 cm, for example, Cat No. 1820 866, Whatman International Ltd., Maidstone, England) were drawn through a trough containing a pre-mixed binder solution that has been further mixed by agitation. The coated paper samples were then sandwiched between two cardboard sheets to absorb excess binder, and pressed between the two cardboard sheets in a Birch Brothers Laboratory Patter set at a speed setting of 5 and at a pressure of 10 psi (68.9476 kPa). The coated sheets were then dried by heating at 90° C. for 90 sec in a vented Mathis oven. Post drying weight was determined to calculate binder add-on (dry binder weight as a percentage of filter paper weight). The dried sheets were then cured in a vented Mathis oven at the times and temperatures specified in Table 2.

The cured sheets were cut into 1 inch (2.54 cm) (cross machine direction) by 4 inch (10.16 cm) (machine direction) strips and tested for tensile strength in the machine direction in a Thwing-Albert Intelect 500 tensile tester. IN tensile strength testing, the fixture gap was set at 2 inches (5.08 cm) and the pull rate was set at 2 inches/minute (5.08 cm/minute). Strips were tested either dry (dry tensile) or immediately after a 10 or 30 minute soak in water at 85° C. (10 min and 30 min wet tensile, respectively.) The tensile strengths in Table 2 were recorded as the peak force measured during parting or breaking each tested strip in two. Each point of the data reported is an average of seven test strips separately tested. TABLE 1 Sample Formulations % Extender on Binder Type Identity A1  0 Standard B1 10 Talc MISTRON ™ 353⁶ B2 20 Talc MISTRON ™ 353⁶ C1 10 Clay¹ ASP ™ 400¹ C2 20 Clay¹ ASP ™ 400¹ D1 10 Silica² IMSIL ™ A-10⁷ D2 20 Silica² IMSIL ™ A-10⁷ E1 10 Silica³ CELITE ™ 281 E2 20 Silica³ CELITE ™ 281 F1 10 Feldspar Minspar 3¹⁰ F2 20 Feldspar Minspar 3¹⁰ G1 10 Kaolin NEOGEN ™ EFP¹¹ G2 20 Kaolin NEOGEN ™ EFP¹¹ A1′  0 Standard G1′ 20 Kaolin NEOGEN ™ EFP¹¹ G3 30 kaolin NEOGEN ™ EFP¹¹ H1 20 Kaolin NEOGEN ™ 2000¹¹ H2 30 Kaolin NEOGEN ™ 2000¹¹ I1 20 1 nm × 200 nm⁴ Montmorillonite I2 30 1 nm × 200 nm⁴ Montmorillonite D2′ 20 Silica² IMSIL ™ A-10⁷ D3′ 30 Silica² IMSIL ™ A-10⁷ J1 20 Clay¹ ASP ™-170¹ J2 30 Clay¹ ASP ™-170¹ K1 20 Silica² SILVER BOND ™ B¹² K2 30 Silica² SILVER BOND ™ B¹² L1 20 Bentonite⁵ BENTOLITE ™ ⁸ L2 30 Bentonite⁵ BENTOLITE ™ ⁸ M  0 ACRONAL ™ 2438 (BASF) N1 20 (ACRONAL ™) Silica² SILVER BOND ™ B¹² N2 30 (ACRONAL ™) Silica² SILVER BOND ™ B¹² O1 20 (ACRONAL ™) Silica² IMSIL ™ A-10⁷ O2 30 (ACRONAL ™) Silica² IMSIL ™ A-10⁷ P1 20 (ACRONAL ™) Bentonite⁵ BENTOLITE ™ ⁸ P2 30 (ACRONAL ™) Bentonite⁵ BENTOLITE ™ ⁸ ¹Anhydrous aluminosilicate clay delaminated Engelhard Corp., Iselin, NJ; (ASP-400 ™: Plates/laminates of mean particle size 4.8 μm; 10% aq. slurry -pH of 4.2; ASP-170 ™: Ultrafloated plates of mean particle size 0.55 μm - 10% aq. slurry- pH of 7.0) ²Microcrystalline silica ³Diatomaceous silica (6 μm mean particle size) ⁴Primary particle size of exfoliated platelets ⁵A colloidal clay comprising montmorillonite ⁶Sierra Talc and Clay Co., Los Angeles, CA ⁷Illinois Minerals Company, Cairo, IL (silica micronized: 2.4 μm mean particle size) ⁸Southern Clay Products, Inc., Gonzales, TX ⁹Johns-Manville Corp., Denver, CO ¹⁰Kentucky-Tennessee Clay Co., Nashville, TN ¹¹Dry Branch Kaolin Co., Dry Branch, GA ¹²Unimin Specialty Minerals Inc., New Canaan, CT (silica micronized - 9 μm mean particle size)

In Table 2, we obtained data on samples prepared with a 30 second cure, which data we do not use to define the ratio of hot-wet tensile strength to dry tensile strength, as used herein. We provided those data simply to show advantages of this invention. TABLE 2 Tensile Strength of Binder and Extended Binder: Tensile Strengths of Treated Glass Microfiber Filter Paper Tensile Strength (lbf) after Tensile Strength (lbf) after 30 sec cure 60 sec cure Cure 10 min 30 min add- 10 min 30 min add- Sample Temp dry wet wet on dry wet wet on A1 210 8.8 6.0 5.0 11.0% 9.0 6.3 5.6 11.0% B1 210 8.6 4.9 4.9 11.3% 8.1 6.2 4.2 11.4% B2 210 9.0 5.4 4.7 11.8% 7.6 6.5 4.8 11.8% C1 210 6.4 5.4 5.4 12.0% 7.2 5.5 4.6 12.3% C2 210 8.0 5.7 5.0 12.2% 6.8 5.8 5.5 12.5% D1 210 8.6 5.6 5.2 12.7% 8.7 5.4 4.8 12.4% D2 210 9.4 5.8 5.1 12.2% 8.6 6.0 5.5 12.3% E1 210 8.3 4.7 4.5 11.2% 8.7 5.7 4.0 11.0% E2 210 9.1 5.9 5.0 11.7% 8.4 6.1 5.0 11.9% F1 210 8.2 5.8 3.3 11.1% 8.8 6.3 4.8 10.7% F2 210 9.0 6.5 3.7 11.2% 8.7 6.9 5.0 10.8% G1 210 8.1 6.2 4.7 11.3% 7.6 6.1 5.3 10.7% G2 210 10.6 5.9 5.3 11.6% 9.3 5.8 5.4 11.6% A1′ 210 10.2 7.5 6.9 10.6% 10.5 7.5 7.0 11.0% G1′ 210 9.2 7.5 6.3 11.6% 9.3 7.4 6.1 11.2% G3 210 9.5 5.5 6.0 12.2% 9.1 6.0 6.0 11.8% A1′ 210 10.2 7.5 6.9 10.6% 10.5 7.5 7.0 11.0% H1 210 9.1 6.1 5.1 14.2% 8.5 6.0 5.8 13.7% H2 210 9.1 5.8 5.2 13.7% 9.2 6.3 5.5 14.2% I1 210 8.6 6.7 5.7 11.1% 9.9 7.4 6.4 10.6% I2 210 8.0 6.9 5.5 10.5 9.4 7.2 6.1 11.2% D2′ 210 9.9 7.9 7.6 13.3 9.1 7.9 7.7 13.8% D3′ 210 7.5 7.4 5.7 14.8% 9.2 7.2 6.3 13.7% J1 210 8.6 7.4 7.2 14.2% 9.6 7.1 6.1 13.7% J2 210 9.9 6.9 6.5 13.6 9.4 7.2 7.4 14.4% K1 210 10.7 7.6 6.8 12.6% 11.0 7.6 7.5 12.5% K2 210 9.6 7.2 7.4 11.8% 9.8 7.7 6.8 13.0% L1 210 10.3 7.9 5.5 11.8% 10.5 8.1 4.7 11.1% L2 210 9.2 7.1 5.5 10.4% 9.4 7.9 4.9 10.7% M 210 9.0 4.5 13.3% N1 210 7.9 3.5 13.0% N2 210 8.3 3.5 12.6% O1 210 8.9 3.9 13.4% O2 210 8.6 4.4 14.4% P1 8.3 3.4 13.1% P2 8.4 2.8 13.3%

Wet tensile strength of a curable composition-treated glass microfiber filter paper which is a substantial fraction of dry tensile strength of a similarly treated glass microfiber filter paper is taken herein to indicate that a composition has cured, and that useful high temperature performance of the cured aqueous composition-treated glass microfiber filter paper results. Extenders that do not alter wet tensile strength by 50% or more are valued for this invention. As shown in Table 3, below, the best hot-wet tensile over dry tensile strengths are shown by the various silicas, especially microcrystalline silica, bentonite, and delaminated aluminosilicate clay, followed by kaolin. Extenders giving the best tensile strength, particularly at high loading, are the various silicas.

We found that upon soaking the paper in the binder solution, we obtained an “add on” of binder to the paper of approximately 11%, but with a small amount of variability. In our definition of “wet over dry tensile strength” we simply perform the soaking as defined, and whatever add on that is obtained is inherent in the test itself. Because we are using a ratio, the slight variability that might result in a measured tensile strength is cancelled out because each of the two strengths in the ratio will have the same variability. Accordingly, the use of a ratio removes much, if not all of the effects of add on variability. Similarly, the use of a ratio approach should remove the effect of slight variations in substrate type (e.g., which type of fiberglass filter paper to use). TABLE 3 *Hot-Wet Strength (30 min. soak at 85° C.)/Dry strength × 100% % Hot- Hot- Example wet/dry wet/dry A1 66.7 0.667 B1 51.9 0.519 B2 63.2 0.632 C1 63.9 0.639 C2 80.9 0.809 D1 55.2 0.552 D2 64.0 0.640 E1 46.0 0.460 E2 59.5 0.595 F1 54.5 0.545 F2 57.5 0.575 G1 69.7 0.697 G2 58.1 0.581 A1′ 66.7 0.667 G1′ 67.8 0.678 G3 65.9 0.659 H1 68.2 0.682 H2 59.8 0.598 I1 64.6 0.646 I2 64.9 0.649 D2′ 84.6 0.846 D3′ 68.5 0.685 J1 63.5 0.635 J2 78.7 0.787 K1 68.2 0.682 K2 69.4 0.694 L1 58.0 0.580 L2 52.1 0.521 M1 50.0 0.500 N1 44.3 0.443 N2 42.2 0.422 O1 43.8 0.438 O2 51.2 0.512 P1 41.0 0.410 P2 33.3 0.333 *Cured at 210° C. for 60 seconds 

1. A curable aqueous composition comprising: 100 weight parts of one or more than one binder chosen from: (i) mixtures of one or more than one polycarboxylic acid or polymeric polyacid, each comprising at least two carboxylic acid groups, anhydride groups or salts thereof, and one or more than one polyol compound having a molecular weight of 1000 or less and comprising at least two hydroxyl groups or epoxy groups, (ii) one or more copolymer or copolymeric polyacid including, as copolymerized units, one or more monomer bearing carboxylic acid groups or anhydride groups, and one or more hydroxyl group-bearing monomer, and (iii) mixtures of (i) and (ii), wherein, the said carboxylic acid groups, anhydride groups or salts thereof are neutralized to the extent of 35% or less with a fixed base, and, further wherein, the ratio of the number of equivalents of the said carboxylic acid groups, anhydride groups or salts thereof in any of the said one or more than one binder to the number of equivalents of the said hydroxyl groups in the same said one or more than one binder is from 1/0.01 to 1/3, and 10 to 40 weight parts of one or more than one extender having an average particle size ranging from 0.5 μm or more and as high as 45 μm or less chosen from microcrystalline silica, diatomaceous silica, kaolin, bentonite, smectite, vermiculite, calcined aluminum silicate, anhydrous aluminosilicate clay delaminated wollastonite, calcium metasilicate, ground glass, nepheline syenite, hydrotalcite, and mixtures thereof, wherein the wet over dry tensile strength of said composition is about 0.5 or greater.
 2. A composition as claimed in claim 1, further comprising one or more phosphorous-containing accelerator.
 3. A composition as claimed in claim 1, further comprising one or more emulsion polymer including, as copolymerized units, greater than 30 wt. %, based on the weight of the emulsion polymer solids, of an ethylenically unsaturated acrylic monomer including one or more C₅ or greater alkyl group.
 4. A composition as claimed in claim 1, wherein the said binder comprises binder (i) and the said polyol comprises one or more epoxy resin.
 5. A composition as claimed in claim 1, wherein the ratio of the hot-wet tensile strength to the dry tensile strength of said composition when cured is about 0.70 or greater.
 6. A composition as claimed in claim 1, wherein the said extender has been screened so as to pass through a screen having a grid size ranging from more than 0.5 μm to 45 μm and so as not to pass through a screen or filter having a grid size or lower resolution limit of 0.5 μm.
 7. A curable aqueous composition comprising: 100 weight parts of one or more than one binder chosen from one or more copolymer or copolymeric polyacid including, as copolymerized units, one or more monomer bearing carboxylic acid groups or anhydride groups, and one or more hydroxyl group-bearing monomer, wherein, the said carboxylic acid groups, anhydride groups or salts thereof are neutralized to the extent of 35% or less with a fixed base, and, further wherein, the ratio of the number of equivalents of the said carboxylic acid groups, anhydride groups or salts thereof in the said one or more than one binder to the number of equivalents of the said hydroxyl groups in the same said one or more than one binder is from 1/0.01 to 1/3, and, 10 to 40 weight parts of one or more than one extender having an average particle size ranging from 0.5 μm or more and as high as 45 μm or less chosen from microcrystalline silica, diatomaceous silica, kaolin, bentonite, anhydrous aluminosilicate clay delaminated, wollastonite, smectite, vermiculite, calcined aluminum silicate, wollastonite, calcium metasilicate, alkali aluminum silicate, ground glass, nepheline syenite, titanium dioxide, zinc oxide, mica, hydrotalcite, and mixtures thereof, wherein the wet over dry tensile strength of said composition is about 0.5 or greater.
 8. A composition as claimed in claim 7, wherein the said extender has been screened so as to pass through a screen having a grid size ranging from more than 0.5 μm to 45 μm and so as not to pass through a screen or filter having a grid size or lower resolution limit of 0.5 μm.
 9. A composition as claimed in claim 7, wherein the said copolymer or copolymeric polyacid further comprises, as copolymerized units, one or more ethylenically unsaturated monomer having a solubility of less than 2 g/100 g of water at 25° C. in the amount of 3 to 25 wt. %, based on the total weight of monomers used to make the curable aqueous binder composition, the said ethylenically unsaturated monomer chosen from ethyl (meth)acrylate, methyl methacrylate, butyl (meth)acrylate, styrene, mono-alkyl (meth)acrylamide, and di-alkyl (meth)acrylamide.
 10. A non-woven heat resistant fibrous substrate coated or impregnated with the cured composition as claimed in claim
 1. 